Polymers with excellent impact strength at ambient and very low temperature are prepared by the polymerization in bulk liquid phase of a vinyl monomer and an olefin trunk polymer of hydrocarbon olefin monomers. The preparation of such polymers is disclosed in detail in U.S. Pat. Nos. 4,071,582; 4,163,033 and 4,169,870, to Takahashi, the disclosures of which are incorporated herein by reference.
The process described in the above-mentioned patents is primarily used at lower proportions of the polyolefin component, up to about 20 weight percent, and preferably up to about 10 weight percent. In the polymerization process, reaction commences with the polyolefin component in solution or partial solution or dispersed in the vinyl monomer. As the reaction proceeds, the reaction mixture thickens to a latex-like consistency. As the conversion progresses, the reaction mixture enters the "paste stage" where it has a dough like consistency. Near the end of the reaction, the polymer mass in the reactor breaks up into discrete particles, which are recovered as the final product. In this process, when the polyolefin component is employed at higher proportions, and when the reaction proceeds to the higher conversions, the reaction product in the thick paste stage does not readily break down into particles. Accordingly, the process is not ordinarily used at proportions higher than about 20 weight percent of the polyolefin component.
The preparation of graft copolymers of unsaturated monomers and polyolefins is also disclosed in U.S. Pat. Nos. 3,289,821 and 3,489,822 to Witt et al. While these patents disclose the reaction of higher proportions of polyolefin, there is no enabling disclose of the reaction being carried out in the bulk liquid phase. Thus, the patentees do not disclose the above described difficulty with respect to breakdown of the reaction mass from a dough-like consistency to discrete particles.
U.S. Pat. No. 3,408,424 to Barkhuff discloses the reaction of vinyl chloride with polyolefins at higher proportions, but the enabling disclosure of this patent is limited to the suspension process and there is no teaching with respect to the bulk liquid phase process. Therefore, the patentees do not disclose encountering the above-described problem with breakdown of a dough-like mass into discrete particles. Barkhuff at col. 5, line 71, teaches that grafting can occur to particles of polyolefin if finely suspended even if not fully dissolved, but he further points out that large rubbery lumps will be evident in the product if dispersing conditions are such as to give more than a small amount of polyolefin in this form. More recently, in U.S. Pat. No. 3,978,162 to Nakanishi, the patentees were still attempting to react polyolefins at higher proportions in a suspension polymerization process much like in the just-described Barkhuff patent.
Severi et al. in U.S. Pat. No. 4,001,349 teach grafting styrene onto an ethylene, propylene, diene modified polymer (EPDM) in a process carried out in aqueous phase for at least part of the reaction. However, the patentees disclose dissolving the EPDM in the styrene monomer and reacting at higher temperatures at the beginning of the process. Likewise, Founier et al U.S. Pat. No. 4,166,081 and Hardt et al U.S. Pat. Nos. 4,276,391 and 4,054,613 teach preparation of polyolefin graft copolymers in solution at higher temperatures and then recovering the products from the solvent.
Lee in U.S. Pat. No. 4,098,734 teaches making graft polymer by dissolving a polybutadiene in monomers than carrying out a reaction in the usual way, eg, suspension, emulsion, bulk or combinations. He teaches that some polybutadiene crosslinks can be used but points out that this may interfere with the required dissolving of the polybutadiene.
Beati et al at J. Applied Polymer Science, Vol. 26, 2185-2195 (1981) disclose reacting methyl methacrylate to an EPR or EPDM rubber in a process in which the EPDM is dissolved. Thereafter the mixture is suspended, the solvent is removed and the monomer is added to form the polymer.
Rademacher in U.S. Pat. No. 3,347,956 teaches a process to convert low density polyethylene into a very fine dispersion in vinyl chloride by heating to a high temperature under agitation and then cooling to form a dispersion of polyethylene in vinyl chloride where the particles have sizes in the 10-200 micron range (col. 4, line 73), more preferably 10-50 microns, and have large surface area. It is not clear whether a uniform graft polymer is made, or whether only a surface reaction occurs. But the patent clearly does not teach that grafting can occur within a large particle, as in the present invention.
Fisher et al. [J. Pol. Sci. Pol. Sym. 66, 443 (1979)] recognize the possibility of reacting ethylenically unsaturated monomers having polar groups such as ester, nitrile, amino, phenyl, ether, and the like, with the surface of polyolefins such as polyethylene, polypropylene and EPDM's in the forms of beads, films, fibres and tubing using monomer, and optionally a swelling agent, with high energy irradiation to surface polymerize or graft to the substrate. Other references to surface reaction (Japan 73/23,357) and a swollen polymer matrix [(Dok) Arad Nauk SSR 229 394 (1976)] have also recognized the possibility of polymerizing on or near the surface of particles or objects. However, they do not disclose or suggest the possibility of absorbing initiator and monomer throughout the particle and polymerizing throughout said particle to make a homogeneous product.
Thus, the prior art teaches making graft coplymers at high proportions of polyolefin but requires that the polyolefin be dissolved in a monomer and the mixture then either be suspended, emulsified or that a solution process take place at a high temperature to give the product. Other art teaches reaction on the surface of particles. The idea of absorption of monomer and initiator into particles which are not soluble in the monomer followed by reaction of the monomer in the particles to give polymer and graft copolymer, which is the subject of this invention, has not be disclosed previously.